OTTAWA (Reuters) - Thousands of revelers, British royals and even Bono will converge on Canada’s capital on Saturday to celebrate the nation’s 150th birthday with a massive party that will be held under a heavy security presence.

About 500,000 people are expected to be in Ottawa for the long-anticipated Canada Day festivities, which will feature a large outdoor celebration in front of the national Parliament, complete with acrobats, fireworks and musicians, including members of Irish rock band U2.

Some cities are celebrating in more unusual ways. Toronto, Canada’s largest city, will have a giant rubber duck floating in its harbor, while Calgary will have a “living flag” composed of people wearing red and white.

Security was already ramped up in the days ahead of the July 1 celebration and party-goers will have to contend with road closures and concrete barriers across entrances into Parliament Hill, located in downtown Ottawa.

National and local police will also be out in force, with security top of mind for many Canadians in the wake of fatal attacks in London, Paris and Germany.

Saturday marks the 150th anniversary of the day Canada officially became a country. Britain had ruled it before 1867.

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The nationwide party comes as Canada is enjoying an unusual amount of interest from the rest of the world, largely due to the election of charismatic and selfie-prone Prime Minister Justin Trudeau.

Still, the planned celebrations have stirred some controversy at home, particularly among First Nations who point to Canada’s history of mistreatment of indigenous people. Activists erected a teepee on Parliament Hill on Thursday in protest.

“As a society, we must acknowledge and apologize for past wrongs, and chart a path forward for the next 150 years,” Trudeau said in a statement ahead of the official kickoff of the celebrations.

Indigenous rights group Idle No More has called for a national day of action on Saturday, telling supporters to hold rallies and take to social media.

Events and installations celebrating the sesquicentennial milestone have already been held across the country this year, with the total cost to the federal government reported to be half a billion dollars.

Along with fireworks, free museums and outdoor concerts nationwide on Saturday, more than 50 special ceremonies to swear in new citizens will be held across the country.

Twitter users were sharing their favorite Canadian songs and food, along with photos of the preparations under the hashtag Canada150.

Trudeau will kick off the opening celebration in Ottawa on Saturday, along with Britain’s Prince Charles and his wife Camilla. The royals began a three-day tour of Canada on Thursday with a trip to the northern territory of Nunavut, home to a large number of First Nations and Inuit people.

The bash in Ottawa will culminate with a musical fireworks show that is billed as largest-ever such display for Canada Day. It will last for 20 minutes and 17 seconds to commemorate 2017.